The rule for inventory deduction is that once a Sales Order is processed, the quantity of inventory should be decreased by the amount of sales order automatically for example You have “Wallet” as a product and the total quantity of available wallets is 15. You processed a sales order of 5 wallets, so the inventory left for the products should be 10 and this is done automatically. But, VTiger does not work like this. In VTiger the deduction in the inventory will only takes place once you generate the invoice. Lets take a practical example to understand this process A company has 20 wallets in stock They processed a sales order of 5 wallets But, Vtiger stills shows 20 wallets in inventory To update the inventory, you will have to generate the invoice. Once, you generate the invoice the inventory available in the products will be reduces by the amount